Few works of historical analysis manage to exert a fundamental influence over an entire field of study. Fewer still continue to do so for the better part of a century. Such, however, is the case with Herbert Grundmann's Religious Movements in the Middle Ages and its pathbreaking identification of the issues framed by its long subtitle - The Historical Links Between Heresy, the Mendicant Orders, and the Women's Religious Movement in the Twelfth and Thirteenth Century, with the Historical Foundations of German Mysticism. In a seminal historicographical article in 1986, John Van Engen declared Religiose Bewegungen to be "the foundation for the historical study of [all] medieval religious life," and in the introduction to the English translation in 1995, Robert Lerner mustered a long list of eminent scholars who placed Grundmann at the very center of their respective fields of study within the history of medieval religion. In 2015, a series of panels that were organized to examine "Grundmann's legacy" at the International Congress on Medieval Studies at the University of Leeds revealed much nuancing and some outright rejection of portions of his arguments, but also much continued utility and vitality.